Visual displays of alphanumeric and graphic information are used on a scale hitherto unknown. The huge amounts of data now being processed on a real-time basis make conventional teletype and video readouts obsolete. Numerous large screen displays enabling simultaneous viewing by a number of users are being developed. Great numbers of light emitting diodes have been used with some degree of success; however, these displays and others usually are unduly complicated, consume great power and are vulnerable to the deleterious effects of the phenomenon known as washout. Washout occurs when an ambient light source is of such an intensity as to make it difficult to discern between activated areas (light areas) and inactivated areas (dark areas) on a display, thus dimishing the contrast. The information content thus is said to be washed out. All who have watched a disappearing picture on a conventional television screen as sunlight shines on it, have been washout.
The vast amounts of data that must be digested and acted upon by scientists and planners, particularly, in situ circumstances, require reliable, relatively uncomplicated visual displays within practical size and weight constraints. One candidate display is disclosed in the pending United States Patent and Trademark Office patent application No. 62,698 and is entitled "Liquid Crystal Fiber Optics Large Screen Display Panel" by Parvis Soltan et al. A liquid crystal panel responsively varies its opacity and images are transmitted to a screen via tapered optical fibers extending from one side of the panel. Alternately, light in front of the screen is reflected from a reflector surface behind the liquid crystal panel, through the fiber optics and back onto the display screen. In this manner, preprogrammed signals fed to the liquid crystal panel determine the information content of the displayed information for a number of viewers. In the close confines of a submersible or an instrument ladened aircraft several scientists and technicians can act on simultaneously presented data and coordinate their work. However, for all its good points, the meritorious capability of this display panel may be compromised by washout. The display operates in either the reflective mode or the transmissive mode and does not totally eliminate washout.
Washout has and continues to be a serious problem in aircraft cockpits. Data representative of navigational inputs, weapons delivery information, aircraft avoidance procedures etc., can be denied due to an operator's inability to discern meaningful information from a display because sunlight or other cockpit light indicators may blot out other meaningful data.
Another electrooptical mechanism for implementing a visual display is disclosed in U.S. Pat. No. 3,840,695 by Albert G. Fisher. The patented invention is entitled "Liquid Crystal Image Display Panel with Integrated Addressing Circuitry" and addresses itself to a matrix of twisted nematic liquid crystals actuated by thin film transistors to provide a flat panel visual readout. A multicolor display is illuminated from the rear by a white light to give a color television display without requiring the bulk of conventional cathode-ray tube arrangements. The relatively thin liquid crystal light valves and their associated polarizers transmit light emanating from the rear of the panel to a number of viewers. However, this unmodified approach operates in the transmissive mode and appears to be vulnerable to the deleterious effects of washout.
Thus, there is a continuing need in the state-of-the-art for a compact, reliable display panel capable of being operated in the transflective mode to avoid the problems otherwise associated with ambient light washout.